In the field of dispensing flexible sheet material from a roll of material, in particular tissue paper towels or tissue toilet paper, different dispenser types are known. In particular, manual dispensers are known in this field which are operated by the respective user by manually pulling the tissue paper towels or tissue toilet paper out of the dispenser. Electric dispensers are also known in this field which dispense the paper towels in reaction to a trigger signal which is used to control an electric motor for feeding the paper. The trigger signal is typically provided by a sensor which senses the presence of a hand of a user, or by a sensor which senses that a towel has just been removed from a dispenser.
Irrespective of whether a manual or electric dispenser is used, one of the issues that are to be considered when designing dispensers of the roll-type arises when the actual roll is about to be depleted and needs to be replaced by a new, full roll. Unlike paper dispensers which dispense stacks of folded tissue paper and which can be easily refilled simply by placing additional paper on top of the almost depleted paper stack, such an easy refill is not available for rolls. In fact, when using rolls, the refilling situation dramatically changes because rolls can only be replaced as a whole.
In particular, for a dispenser which is designed for a single roll of material, the service personnel which services the respective premises needs to be alerted in a timely manner to replace the almost depleted roll of material in order to make sure that the users of the respective bathroom are always in a position to dry their hands or to have a sufficient supply of toilet paper available.
For dispensers which are designed to hold two or more rolls of material, namely the actually dispensed roll of material and replacement roll(s), a replacement roll needs to replace a depleted roll at the right timing. In particular, a triggering mechanism which is responsible for replacing the depleted roll has to be reliable, such that the exchange of rolls is carried out smoothly and at an efficient and economically sensible timing. In particular, for economical and ecological reasons, it is desirable to fully use-up a roll of material before the replacement roll is set in place to be dispensed.
In order to accomplish this and in order to determine when the roll is depleted and needs to be replaced, US 2003/0078691 A1 suggests counting the number of rotations of the roll and calculate from this the actual usage of the dispensed paper. However, it becomes immediately apparent that, in order to be in a position to correctly calculate the amount dispensed on the basis of the rotations and to determine from this information the actual filling status of the roll, the dimensions of the roll as well as those of the material need to be accurately known. In particular, the calculation is extremely sensitive to small deviations in the thickness of the material, to the diameter of the winding core, and to the actual length of the paper on this particular roll. Accordingly, the set-up suggested in this publication needs to be supplied with quite a number of data for each type of paper.
In U.S. Pat. No. 4,901,663, a different solution is suggested, according to which printed marks are provided to the end face of the towel roll. On the basis of these marks, the upcoming end of the roll can be determined. However, the step of printing marks onto the end face of the roll requires additional equipment and yet another step in the manufacturing process of the paper, because the marks can only be printed onto the end face after the log has been cut into individual rolls.